Many different technologies have been developed for fabricating switches and relays for low frequency and high frequency switching applications. Many of these technologies rely on solid, mechanical contacts that are alternatively actuated from one position to another to make and break electrical contact. Unfortunately, mechanical switches that rely on solid—solid contact are prone to wear and are subject to a condition known as “fretting.” Fretting refers to erosion that occurs at the points of contact on surfaces. Fretting of the contacts is likely to occur under load and in the presence of repeated relative surface motion. Fretting typically manifests as pits or grooves on the contact surfaces and results in the formation of debris that may lead to shorting of the switch or relay.
To minimize mechanical damage imparted to switch and relay contacts, switches and relays have been fabricated using liquid metals to wet the movable mechanical structures to prevent solid to solid contact. Unfortunately, as switches and relays employing movable mechanical structures for actuation are scaled to sub-millimeter sizes, challenges in fabrication, reliability and operation begin to appear. Micromachining fabrication processes exist to build micro-scale liquid metal switches and relays that use the liquid metal to wet the movable mechanical structures, but devices that employ mechanical moving parts can be overly-complicated, thus reducing the yield of devices fabricated using these technologies. Therefore, a switch with no mechanical moving parts may be more desirable.
In some applications, such as high frequency switching, liquid metal switches can provide poor isolation. A signal that is supposed to be isolated by the open contacts of the switch can leak across the open contacts, causing intermittent errors and unintended results. Lack of reliable isolation results in lack of circuit reliability.
It would be desirable to have a three-stage liquid metal switch that would overcome the above disadvantages.